The present invention relates to singling out and individually depositing grains such as individual seeds. Thus, the invention relates specifically, but not exclusively, to a planter.
Machines and devices are known by means of which individual grains such as seeds are placed, e.g., on the ground, a furrow, or the like, and in as accurate a mutual spacing as possible. These devices operate mechanically or by means of pneumatics. Pneumatic devices operate with suction as well as pressurized air. A single seed planter is, for example, disclosed in U.S. Pat. No. 3,715,057, now reissued. The planter, as described in this patent, includes a wheel or drum, having peripherally arranged, funnel-shaped compartments. The narrow opening of such a funnel is smaller than the smallest grain. Upon blowing air into such a compartment, one--and only one--grain is kept therein by a combination of suction and dynamic pressure; all other grains, which may have been picked up by the compartment, will be blown out again. As the drum turns, a compartment occupied by one grain is moved into a zone in which the grain is removed from the compartment and, e.g., placed onto the ground (see also U.S. Pat. No. 3,913,503). The path of the drum is particularly determined, and there are additional means to permit the grain to fall out of its compartment from one particular position only of that drum.
The above-mentioned device operates quite successfully. It was found, however, that the speed of operation, i.e., the speed of the drum, is somewhat limited. The reason for this is to be seen here in the point that a fast moving drum tends to impart a tangential movement upon the seed and, so to speak, throws the grain down. In the case of low speeds, this presents no particular problem; in the case of high speeds, the seed may easily tend to roll away, so that the various seeds are irregularly planted. The worm screw-depositing device as per my German patent No. 3,912,503 is limited in speed by the nature of its structure.